Low emissivity coating with low solar heat gain coefficient, enhanced chemical and mechanical properties and method of making the same

ABSTRACT

The invention provides low-emissivity stacks being characterized by a low solar heat gain coefficient (SHGC), enhanced aesthetics, mechanical and chemical durability, and a tolerance for tempering or heat strengthening. The invention moreover provides low-emissivity coatings comprising, in order outward from the substrate a first dielectric layer; a first nucleation layer; a first Ag layer; a first barrier layer; a second dielectric layer; a second nucleation layer; a second Ag layer; a second barrier layer; a third dielectric layer; and optionally, a topcoat layer, and methods for depositing such coatings on substrates.

FIELD OF THE INVENTION

The present invention relates generally to low emissivity (“low-e”)coatings, and more particularly to coatings with low solar heat gaincoefficient (SHGC) (“low-g”) and retained or enhanced mechanical andchemical durability.

BACKGROUND OF THE INVENTION

All United States Patents and patent applications referred to herein,including copending U.S. application Ser. No. 11/648,913, U.S.application Ser. No. 11/431,915, U.S. Provisional Application No.60/680,008, U.S. Provisional Application No. 60/736,876, and U.S.Provisional Application No. 60/750,782, are hereby incorporated byreference in their entireties. In the case of conflict, the presentspecification, including definitions, will control.

Solar control coatings on transparent panels or substrates are designedto permit the passage of visible light while blocking infrared (IR)radiation. High visible transmittance, low emissivity coatings on, e.g.,architectural glass and automobile windows can lead to substantialsavings in costs associated with environmental control, such as heatingand cooling costs.

Generally speaking, coatings that provide for high visible transmittanceand low emissivity are made up of a stack, which typically includes atransparent substrate and an optical coating. The stack includes one ormore thin metallic layers, with high IR reflectance and lowtransmissivity, disposed between anti-reflective dielectric layers.These systems reflect radiant heat and provide insulation from the coldas well as from solar radiation. Most low-e stacks in use today arebased on transparent dielectrics. In general, the thickness of thedielectric layers are tuned in to reduce inside and outside reflectanceso that the light transmittance is high (>60%). The IR reflectivemetallic layers may be virtually any reflective metal, such as silver,copper, or gold. Silver (Ag) is most frequently used for thisapplication due to its relatively neutral color. The anti-reflectivedielectric layers are generally transparent material selected to enhancevisible transmittance.

Conventional low emissivity coatings generally strive to maintainreflection relatively constant throughout the visible spectrum so thatthe coating has a “neutral” color; i.e., is essentially colorless.However, conventional low-emissivity coatings fail to provide theextremes of reflected color required for aesthetic and other reasons bycertain applications.

To achieve the desired properties in a coated substrate, the compositionand thickness of each of the layers of a multilayer coating must bechosen carefully. For example, the thickness of an IR reflective layer,such as Ag, must be chosen carefully. It is well known that theemissivity of a Ag layer tends to decrease with decreasing Ag sheetresistance. Thus, to obtain a low emissivity Ag layer, the sheetresistance of the Ag layer should be as low as possible. However,increasing Ag layer thickness will also cause visible transmission todecrease and can result in colors that are generally undesirable. Itwould be desirable to be able to increase visible transmission bydecreasing Ag layer thickness without increasing sheet resistance andemissivity.

Thin, transparent metal layers of Ag are susceptible to corrosion whenthey are brought into contact, under moist or wet conditions, withvarious corrosive agents, such as atmosphere-carried chlorides,sulfides, sulfur dioxide and the like. To protect the Ag layers, variousbarrier layers can be deposited on the Ag. However, the protectionprovided by conventional barrier layers is frequently inadequate.

Coated glass is used in a number of applications where the coating isexposed to elevated temperatures. For example, coatings on glass windowsin self-cleaning kitchen ovens are repeatedly raised to cookingtemperatures of 120-230° C., with frequent excursions to, e.g., 480° C.during cleaning cycles. In addition, when coated glass is tempered orbent, the coating is heated along with the glass to temperatures on theorder of 600° C. and above for periods of time up to several minutes.These thermal treatments can cause the optical properties of Ag coatingsto deteriorate irreversibly. This deterioration can result fromoxidation of the Ag by oxygen diffusing across layers above and belowthe Ag. The deterioration can also result from reaction of the Ag withalkaline ions, such as sodium (Na+), migrating from the glass. Thediffusion of the oxygen or alkaline ions can be facilitated andamplified by the deterioration or structural modification of thedielectric layers above and below the Ag. Coatings must be able towithstand these elevated temperatures. However, previously knownmultilayer coatings employing Ag as an infrared reflective filmfrequently cannot withstand such temperatures without some deteriorationof the Ag film.

Low emissivity coatings are described in U.S. Pat. Nos. 4,749,397 and4,995,895. Vacuum deposited low emissivity coatings containing silverare presently sold in the fenestration marketplace.

U.S. Pat. No. 4,995,895 teaches the use of oxidizable metals as hazereduction topcoats useful for protecting temperable low-e coatings. Thispatent is directed to methods of reducing haze resulting from exposureto temperatures over 600° C.

Metal, metal alloy and metal oxide coatings have been applied to lowemissivity silver coatings to improve some properties of the coatedobject. U.S. Pat. No. 4,995,895 describes a metal or metal alloy layerwhich is deposited as the outermost layer of the total layers applied toa glass base. The metal or metal alloy layer is oxidized and acts as ananti-reflection coating. U.S. Pat. No. 4,749,397 describes a methodwhere a metal oxide layer is deposited as an antireflection layer.Sandwiching the silver layer between anti-reflection layers optimizeslight transmission.

Unfortunately, optical coatings are frequently damaged during shippingand handling, including by scratching and by exposure to corrosiveenvironments. Silver based low-emissivity coatings are particularlysusceptible to corrosion problems. Most low emissivity stacks in usetoday make use of barrier layers somewhere in or on the low emissivitythin layer stack to reduce these problems. Thin barriers typicallyfunction to reduce the corrosion of silver layers from water vapor,oxygen or other fluids. Some reduce damage from physical scratching ofthe low emissivity stack by virtue of their hardness or by loweringfriction if they form the outer layer.

For sub-desert areas as well as regions with an intense sun load, thecurrent high transmittance low-e products are already bringingadvantages, but the heat and light load is still too high to maximizethe thermal and visual comfort inside the houses and buildings in whichsuch low-e products are being used.

A few low-e stacks with lower light transmittance are available, butsuch products usually exhibit at least one of the following draw backs:high reflectance, which makes them less aesthetically appealing, or highshading coefficient, which makes them inappropriate for controlling theheat load.

Very few commercially available low-e products combine the desiredoptical properties and shading coefficient. Those that do still requireadditional modifications to make them ideal for processing andproduction. Further, such low-e coatings are soft coatings that requireextra attention during storage and processing into an insulating glassunit. It is desirable to improve the current mechanical and chemicaldurability of such coatings.

Producing different stack designs on the same coater also can oftenpresent a problem because the set-up requirements are not alwayscompatible between the different designs. It would be desirable toprovide different coatings that can be produced simultaneously on acoater without requiring down time and modification of the coaterlayout.

Furthermore, for safety reasons, more glass is now being heat treated toincrease its mechanical strength and avoid laceration in case ofbreakage. This is especially true for low SHGC products. The increase inenergy absorption of the coating increases the potential thermal stresson the lite when part of it is exposed to the sun's radiation and partof it is in the shade. Typical low-e coatings are not designed towithstand thermal strengthening or tempering. Such conditions cancompletely damage the coating, destroying its aesthetic appeal, therebyrendering it unusable.

There thus remains a need for low emissivity coating stacks (and methodsof making them) that overcome the various problems seen in the priorart. In particular, there is a need for low-e stacks having a low solarheat gain coefficient, which stacks exhibit retained or increasedaesthetic appeal, and mechanical and/or chemical durability, and whichcan be tempered or heat strengthened, if desired. Moreover, there is aneed for stacks that can be applied without need for a specific,nonstandard coater.

SUMMARY OF INVENTION

To overcome the problems associated with previous low emissivitycoatings, the present invention provides improved coatings that yieldstacks that have a low solar heat gain coefficient (i.e., low-g stacks),are aesthetically appealing, and exhibit equal or better chemical andmechanical durability than typical low emissivity stacks. Moreover, theinvention provides products which are compatible with standardproduction methods. In particular, for example, shifting from a standardcoater to a low-g coater would not require venting or other change incoater layout. Furthermore, glass substrates coated in accordance withthe invention surprisingly can be tempered or heat strengthened withoutsuch tempering or heat strengthening causing degradation in the stacklayers or in the optical qualities of the coated substrate and withoutcausing the other drawbacks typically seen when such processes are usedin connection with low emissivity coatings.

The present invention overcomes the disadvantages seen in low e stacksknown in the art by increasing the absorption of such stacks, throughthe introduction of at least one thin absorbing layer, or by increasingthe absorption of other layers, such as barrier layers. Such techniquesfor increasing the absorption of the stack decrease the overall lighttransmittance without increasing the light reflectance. Such increasedlight reflectance is frequently a problem, particularly when it occurson a pane facing the inside of a building.

The appropriate choice of absorbing material also enables one to controlthe transmittance color of the coated glass. In embodiments, anabsorbing layer can be inserted between a barrier layer protecting aninfrared reflecting layer, and an overlying dielectric. In alternateembodiments, a barrier layer itself can be made more absorbing toachieve a similar result. In such embodiments, the barrier layer thusserves both as a barrier layer and as an absorbing layer and is referredto herein as an “absorbing barrier” layer. The infrared reflecting layeris preferably silver (Ag), but may be any reflective material, such as,without limitation, copper or gold. Accordingly, in an aspect, theinvention provides a low-emissivity coating on a substrate, the coatingcomprising, in order outward from the substrate, a first dielectriclayer; a first infrared reflecting layer; a first absorbing barrierlayer; a second dielectric layer; a second infrared reflecting layer; asecond absorbing barrier layer; a third dielectric layer; andoptionally, a topcoat layer. The optional topcoat layer is employed inembodiments which are to be subjected to tempering or heat treatment. Inpreferred embodiments, a nucleation layer underlies one or both of theinfrared reflecting layers. While preferred embodiments include theabove stack configurations, the invention also provides coatings havinga single infrared reflecting layer, rather than two or more such layers.Such embodiments therefore would include a first dielectric layer;optionally, a nucleation layer; an infrared reflecting layer; anabsorbing barrier layer; a second dielectric layer; and, optionally, atopcoat layer. The coatings of the present invention are formed bydepositing the layers onto the substrate. A preferred method includesdepositing by magnetron sputtering.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an embodiment of an aesthetically appealinglow-emissivity stack, exhibiting low SHGC and enhanced mechanical and/orchemical durability in accordance with the present invention.

FIG. 2 depicts an alternate embodiment of an aesthetically appealinglow-emissivity stack, exhibiting low SHGC and enhanced mechanical and/orchemical durability, which includes nucleation layers for improving theproperties of the Ag layers, in accordance with the present invention.

FIG. 3 depicts a further embodiment of an aesthetically appealinglow-emissivity stack, exhibiting low SHGC and enhanced mechanical and/orchemical durability in accordance with the present invention.

FIG. 4 depicts a still further embodiment of an aesthetically appealinglow-emissivity stack, exhibiting low SHGC and enhanced mechanical and/orchemical durability in accordance with the present invention.

FIG. 5 depicts an embodiment of a low emissivity stack for use in anautomotive or other vehicle, including two glass substrates, a PVBlayer, and a coating in accordance with the present invention.

FIGS. 6A and 6B depict optical constant data for typical materialssuitable for use as low-g absorbers in accordance with the invention.FIG. 6A provides data relating to the index of refraction (n) and FIG.6B provides data relating to extinction coefficient (k).

FIG. 7 provides graphical data illustrating index of refraction andextinction coefficients for two stoichiometries of SiAlOxNy.

FIG. 8 provides graphical data illustrating preferred n & k values forSiAlOxNy in low-g stacks in accordance with the invention.

FIG. 9 depicts an alternate embodiment of an aesthetically appealinglow-emissivity stack, exhibiting low SHGC and enhanced mechanical and/orchemical durability in accordance with the present invention.

FIG. 10 depicts a further embodiment of an aesthetically appealinglow-emissivity stack, exhibiting low SHGC and enhanced mechanical and/orchemical durability in accordance with the present invention.

FIG. 11 depicts an embodiment of an aesthetically appealinglow-emissivity stack, exhibiting low SHGC and enhanced mechanical and/orchemical durability in accordance with the present invention.

FIG. 12 depicts an alternate embodiment of an aesthetically appealinglow-emissivity stack, exhibiting low SHGC and enhanced mechanical and/orchemical durability, which includes nucleation layers for improving theproperties of the Ag layers, in accordance with the present invention.

FIG. 13 depicts a further embodiment of an aesthetically appealinglow-emissivity stack, exhibiting low SHGC and enhanced mechanical and/orchemical durability in accordance with the present invention.

FIG. 14 depicts a still further embodiment of an aesthetically appealinglow-emissivity stack, exhibiting low SHGC and enhanced mechanical and/orchemical durability in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description, reference is made to variousspecific embodiments in which the invention may be practiced. Theseembodiments are described with sufficient detail to enable those skilledin the art to practice the invention, and it is to be understood thatother embodiments may be employed, and that structural and logicalchanges may be made without departing from the spirit or scope of thepresent invention.

The present invention provides improved coatings that yield lowemissivity stacks that have a low solar heat gain coefficient (SHGC),are aesthetically appealing, and exhibit equal or better chemical andmechanical durability than typical low emissivity stacks. Moreover, theinvention provides products which are compatible with standardproduction methods. In particular, for example, shifting from a standardcoater to a low-g coater would not require venting or other changes incoater layout. Furthermore, glass substrates coated in accordance withembodiments of the invention surprisingly can be tempered or heatstrengthened without the drawbacks typically seen when such processesare used in connection with low emissivity coatings.

In embodiments, the present invention achieves the desired properties oflow-e stacks by increasing the absorption of such stacks, through theintroduction of at least one thin absorbing layer, or by increasing theabsorption of other layers, such as barrier layers, (thereby yielding“absorbing barrier” layers). Such techniques for increasing theabsorption of the stack decrease the overall light transmittance withoutincreasing the light reflectance. Such increased light reflectance isfrequently a problem, particularly when it occurs on a pane facing theinside of a building. Tolerance for tempering can be enhanced byadjusting the thickness of the dielectric or absorbing barrier layers orthe nature of the absorbing barrier layers.

In an aspect, the invention provides a low-emissivity stack, including acoating on a substrate, the coating comprising at least one absorbinglayer. The absorbing layer can be a layer that is present in addition toa barrier layer. Alternatively, a barrier layer can be modified to alsoact as an absorbing layer, thus becoming an absorbing barrier layer andeliminating the need for separate absorbing and barrier layers. Thelow-emissivity stack is characterized by a solar heat gain coefficient(SHGC) that is less than about 0.34, preferably less than about 0.31. Insome embodiments, the low-e stack is characterized by a SHGC of about0.22 to about 0.25. In various embodiments, the stack has a lighttransmittance of about 42% to about 46%. In some embodiments describedherein, the light transmittance can be up to about 62%. Duringtempering, the transmittance rises by about 1-8%. In some embodiments,the stack has a transmittance color with a negative a* and a negativeb*. In alternate embodiments, the stack has a transmittance color with anegative a* and a positive b*.

In an aspect, the invention provides a low-emissivity coating on asubstrate, the coating comprising, in order outward from the substrate,a first dielectric layer; a first infrared reflecting layer; a firstabsorbing barrier layer; a second dielectric layer; a second infraredreflecting layer; a second absorbing barrier layer; a third dielectriclayer; and optionally, a topcoat layer. Either of the first or secondabsorbing barrier layers is optional, i.e., two such layers are notrequired. The optional topcoat layer is employed in embodiments whichare to be subjected to tempering or heat treatment. In preferredembodiments, a nucleation layer underlies one or more of the infraredreflecting layers.

The substrate is preferably glass. In preferred embodiments, the twoinfrared reflecting layers are Ag layers and are well balanced with aratio Ag1/Ag2 of about 80% or higher. However, in alternate embodiments,the ratio may be as low as 50%. Having balanced Ag layers providesvarious advantages, in particular from a process point of view. Becausethe two targets erode at approximately the same rate, the length of acampaign can be maximized. When the second Ag layer (Ag2) is muchthicker than the first one (Ag1), for example, the coater must be ventedearly in the campaign, which has a strong negative impact on productioncost. As noted above, the invention also provides coatings having asingle Ag layer, rather than two or more Ag layers.

The absorbing layer, when present as a separate layer, is preferablyinserted between the barrier protecting the Ag layer and the overlyingdielectric. The absorbing material can include a metal, an alloy, asilicide, an absorbing oxide, an absorbing gray metal, a nitride, or anyother suitable material that achieves the desired effect. Preferredmaterials include, without limitation, Ti, TiN, Si, NiCr, NiCrOx, Cr,Zr, Mo, W, and ZrSi, nickel or chromium alloys, and transition metals,nitrides, subnitrides, and suboxides thereof, as well as silicides andaluminides. In preferred temperable and non-temperable embodiments, theabsorbing material comprises NiCr. In some embodiments which are not tobe tempered, Ti also works well as an absorbing material.

The appropriate choice of absorbing material also enables one ofordinary skill to control the transmittance color of the coated glass. Aneutral color (a* and b* negative and well balanced are preferred—theminimal requirement being a negative a* value and a b* value that islower than +2 for transmittance and glass side reflectance) is moreaesthetically appealing than a stronger greenish or yellowish hue. Aneutral transmittance is highly desirable because it maximizes thecorrect color rendering of the insulated glass unit (IGU) housing theglass. The present invention also makes it possible to obtain a bluishhue, if desirable.

Thus, certain materials in low-g designs have been found capable oflowering transmission of low-e coatings and allowing the stack color tobe tuned to preferred colors. In the case of temperable coatings, thepreferred materials also are thermally stable within the thin filmstack. Many other materials can be used as alternatives to the absorbingmaterials recited above. Such materials are those which can be definedby a range of index of refraction (n) and extinction coefficients (k)that are suitable for performing this transmission lowering function. Ina temperable low-g design, the absorbing layer will have the appropriateoptical properties as well as additional thermal stability properties.

When a separate absorbing layer is not employed, one or more barrierlayers can be modified to achieve increased absorption, therebyresulting in the same desirable optical properties described above. Suchmodification preferably includes altering gas levels in these layers, asrepresented in the graphs below. These graphs show the relationshipbetween NiCrOx oxygen flow to sputter power (kilowatts) and NiCrOxextinction coefficient (k). The second y scale also shows TY or SHGCvalues when the given NiCrOx is used in a double silver low-e stack asdescribed herein.

The NiCrOx ratio preferably is based on 2879 mm long sputtering targetsrun with DC power. Power is typically in the range from 15 to 45 kw.Argon flow is 300 sccm.

U.S. Pat. No. 6,416,872, incorporated into this application by referencein its entirety, refers to the use of a solar control design thatcontains a Fabry-Perot type thin film stack (metal/dielectric/metal).One of the metals is an infrared reflecting material (silver) and one isan optically absorbing material. The optically absorbing material isdescribed in terms of a range of suitable optical constants. Embodimentsof the present invention similarly include Fabry-Perot stacks butcomprise a general layer structure of metal/metal/dielectric/metal/metalor, more specifically, metal/thin suboxide absorber(barrier)/metal/dielectric/metal/thin suboxide absorber (barrier)/metal.In each of these cases, one metal of the metal/metal pair is preferablyan infrared reflecting metal and the other is preferably an absorbingmetallic material. The low-g absorbing metallic material may bedescribed by optical constant ranges similar to those set forth in U.S.Pat. No. 6,416,872. Optical constants for typical materials opticallysuitable as low-g absorbers are plotted in FIGS. 6A and 6B. Based on thedata presented in FIG. 6A, the preferred index of refraction range at awavelength of 550 nm is from about 1 to about 5.5 for the metallicabsorbers shown. Based on the data presented in FIG. 6B, the extinctioncoefficient range at a wavelength of 550 nm is from about 1.75 to about4.5 for the metallic absorbers shown. An additional parameter that maybe used in helping to define the range of suitable materials is that ofan index plot which has a positive slope at 550 nm. This characteristicwould distinguish the metallic materials from suboxides and nitrideswhich, when similarly plotted, typically have a negative slope at 550nm.

In an embodiment of the invention, the absorbing layer, when present asa separate layer, is introduced in a very specific location in thestack. This is to optimize the other properties which are important forthe manufacturing and the processing of the coated glass, particularlythe overall durability and the ease of production.

Each of the absorbing layers, when present, preferably has a thicknessof about 0.1 nm to about 8 nm. If two absorbing layers are included, thefirst absorbing layer preferably is thicker than the second absorbinglayer. The first absorbing layer preferably has a thickness of about 1nm to about 6 nm, more preferably 1.5 nm to about 5 nm. The secondabsorbing layer preferably has a thickness of about 0.1 nm to about 5nm, more preferably about 0.1 nm to about 4 nm. In an alternateembodiment, the first absorbing layer has a thickness of about 3 nm. Inanother alternate embodiment, the second absorbing layer has a thicknessof about 0.5 nm. In another alternate embodiment, the first absorbinglayer has a thickness of about 3.6 nm. In another alternate embodiment,the second absorbing layer has a thickness of about 0.1 nm. Theabove-noted thickness ranges are similarly suitable for absorbingbarrier layers when such layers are used in lieu of separate absorbingand barrier layers.

The barrier layer (whether separate or an absorbing barrier layer)protects the Ag layer against attack of the plasma when sputtering thedielectric on top of it. It also improves the chemical durability bycontrolling the diffusion of aggressive species like O₂, O, H₂O, andNa+. In a preferred embodiment, the barrier is transparent. The barriercan comprise, without limitation, NiCr, NiCrOx, TiOx, NiCrNxOy, NiCrNx,Ti or other metal or metals, or subnitrides or suboxides thereof. Apreferred barrier is NiCrOx. In such layers, particularly in the first(i.e., bottom) NiCrOx layer, it may comprise approximately 15 to 60atomic percent oxygen. Preferably, the atomic percent oxygen is from 20%to 55%. Thermal durability for the temperable versions of this inventionwas improved when the first NiCrOx layer contained about 20 atomicpercent oxygen. In preferred embodiments, (particularly when the barrieris modified to also have increased absorbing qualities), the barriercomprises NiCrOx and is a thin protective layer sputtered on silver anddeposited from planar targets. It is preferably sputtered in anargon-oxygen mixture. The power to oxygen flow (sccm) is the preferredmethod used to estimate oxidation in sputtered NiCrOx. The ratio usedfor fully oxidized NiCrOx is 10:1. The ratio used in some coatings inaccordance with the inventions preferably varies from 7.5:1 to 8.0:1.

In alternate preferred embodiments, an absorbing barrier of NiCr isemployed. Similarly, this thin protective barrier layer is preferablysputtered on silver and deposited from DC planar targets. In suchembodiments, the NiCr layer (or layers) are sputtered in argon only.Such NiCr layers can be fully metallic except for unitentionalimpurities, such as may be caused by gas crosstalk from neighboringcathodes.

In preferred embodiments, the dielectric layers each independentlycomprise an oxide, a nitride, or an oxy-nitride. When a dielectric layercomprises an oxide, the oxide is preferably sputtered from a Ti, a Zn,an Sn, a ZnSn alloy, or a Bi target. The oxide may comprise Nb₂O₅. Theoxide may comprise up to about 20 wt %, preferably up to about 10 wt %of an element, such as Al or B, or similar such element. These dopantsare commonly used to make silicon coater targets conductive. When adielectric layer comprises a nitride or an oxy-nitride, the nitride oroxy-nitride can be a nitride or oxy-nitride of Si, SiAl, SiB, SiZr, orother suitable nitride or oxy-nitride that achieves the desired effect.Similarly, the nitride or oxy-nitride may comprise up to about 20 wt %,preferably up to about 10 wt % of an element, such as Al or B, orsimilar such element for making the coater target conductive. Inpreferred embodiments, the dielectric is SiAlOxNy and is reactivelysputtered from a silicon/10 weight percent aluminum rotatable cathode.The reactive gas is preferably about 90% nitrogen flow and 10% oxygen.Although stoichiometry variations occur from layer to layer and fromproduction run to production run, the material is preferablysub-stoichiometric. In preferred embodiments, insufficient nitrogen andoxygen are present in the sputtering gas for the SiAl to reach a fullyreacted oxy-nitride. In some embodiments, atomic ratios in the layer areapproximately Si₄O_(0.4)N₅.

In preferred embodiments that employ three primary dielectrics, at leastone of the dielectric layers is in a substoichiometric state. Morepreferably, all three such dielectrics (e.g., SiAlOxNy) are in asubstoichiometric state. Various advantages can be achieved using suchsubstoichiometric layers. For example:

1. The deposition rate from SiAl sputter targets is higher if the targetsurface chemistry is sub-stoichiometric. Sputter yield for a siliconrich surface is higher than for a surface comprised of more nitridedsilicon. The higher deposition rate is advantageous for running a coaterat higher speeds, which is more economical.

2. The higher index of the sub-stoichiometric nitrides allows fordielectric layers that have a lower physical thickness for the sameoptical thickness. Less target material is consumed whensub-stoichiometric layers are deposited and again, this allows thecoater to run more efficiently.

3. The higher index dielectrics allow for greater flexibility in theoptical characteristics in the low-e stack design. Desirable colors fortransmission and reflection may be more easily achieved using higherindex dielectrics than can be achieved using lower index, stoichiometricmaterials.

4. Sub-stoichiometric layers tend to have better chemical barrierproperties than stoichiometric dielectrics. This allows for a morechemically stable and corrosion resistant low-e stack. Corrosivechemicals are less likely to reach the vulnerable silver layers.

5. The optical absorption of the sub-stoichiometric dielectrics helpsreduce the transmission and raise the solar heat gain coefficient of thelow-g stack. Sub-stoichiometric dielectrics tend to be opticallyabsorbing in the visible and more transparent in the infrared. Thus,these materials reduce visible transmission but do not tend to interferewith the infrared reflective properties of the silver layers.

Metal absorber layers are optically absorbing in both visible andinfrared. When metallic materials are used to reduce transmission in alow-g product, both visible transmission and infrared reflection arereduced. It is desirable for low-e products to have as high an infraredreflection as possible.

These advantages tend to occur for sub-stoichiometric oxides,oxy-nitrides, and nitrides which might be used in a low-e stack.

The silicon to aluminum ratio used in the preferred dielectrics instacks in accordance with the invention is 10 weight % Al. Other Si:Alratios may be used. In some embodiments, the atomic ratio of Si, O, andN is approximately Si₄O_(0.4)N₅. The top silicon oxynitride dielectrichas a primary function as an optical interference layer, whichcontributes to the antireflection of the silver. The material is chosen,however, in part for its barrier properties and hardness, and itcontributes to the protection of the silver, both mechanically andchemically.

FIG. 7 depicts Index and Extinction coefficients for siliconoxy-nitride. The indices and extinction coefficients plotted on thegraph show two stoichiometries of SiAlOxNy. These represent theapproximate SiAlOxNy stoichiometry upper and lower limits that would besuitable for low-g coatings. Stoichiometry for the preferred embodimentstypically would fall between these two extremes. FIG. 8 depictsapproximate preferred n & k values for SiAlOxNy in low-g stacks.

In preferred embodiments, the dielectrics have indices of refraction at550 nm that are between about 1.8 and about 2.5, more preferably betweenabout 2.1 and about 2.3. Specifically, in preferred embodiments, the topdielectric may have a lower index of refraction than the bottom ormiddle dielectrics. In such embodiments, the top dielectric has an indexof refraction between about 1.8 and about 2.3 and the bottom or middielectrics have an index of refraction between about 2.0 and about 2.5.In preferred embodiments, the dielectrics have extinction coefficientsat 550 nm that are between about 0 and about 0.05, more preferablybetween about 0.01 and about 0.02.

In preferred embodiments, the coating further comprises a nucleationlayer between the first dielectric layer and the first Ag layer. In analternate preferred embodiment, the coating further comprises a secondnucleation layer between the second dielectric layer and the second Aglayer. The nucleation layers improve the properties of the Ag layer, andare typically based on Zn oxide, with up to about 15 wt % of otherelements, such as, without limitation, Al, Sn, or a combination thereof.In preferred embodiments, the sputtering targets used to deposit ZnOcontain approximately 1.5% Al, yielding layers that are ZnAlOx. Thismaterial preferably is reactively sputtered from a zinc/1.5 weightpercent aluminum rotatable or planar cathode. The sputtering gaspreferably consists of argon and sufficient oxygen for the oxide to bedeposited in a fully oxidized state. Nucleation layers for silver, suchas those described herein, are commonly described in low-e patentliterature. The nucleation layers in embodiments of the presentinvention are preferably between about 2 nm and 12 nm in thickness. Inpreferred embodiments, the bottom nucleation layer is thicker than thetop nucleation layer, with the ratios between the two being about 1.2 toabout 2.0. This configuration improves durability, particularlyfollowing heat treatment or tempering.

In preferred embodiments, the infrared reflecting layers comprise Ag andare sputtered in pure argon. Alternatively, a small amount of oxygen maybe added. The oxygen helps with mechanical durability, particularly inembodiments subjected to heat treatment or tempering.

The optional topcoat, if included, can have a positive impact on thechemical and/or mechanical stability. It can comprise, withoutlimitation, C, SiSn, ZrSi, SiSnO₂ or silicides. It should be noted thatthis nomenclature is not intended to refer to the stoichiometry oratomic ratio of the different elements. For example, ZrSi is a sputteredmaterial in which the Zr at % varies from 0 to 100% and the layer can begraded. This layer may oxidize upon heating. The topcoat typically has acontrasting nature compared to the underlying dielectric. If thedielectric is an oxide, the topcoat is preferably one of the abovematerials, or a nitride or an oxynitride, such as SiN or SixAlyNzOc.Alternatively, when the dielectric is a nitride or an oxynitride, thetop coat is chosen from the above list, or can be an oxide (for instanceZrO₂, ZrSiO₂, SnO₂, or, ZrOxNy, TiO₂ or other similar substance, but notlimited to the precise stoichiometric ratios recited herein). Apreferred topcoat is carbon, and is used preferably in a temperableproduct during production. Such a coating, which is typically sputtered,is preferably about 4-8 nm thick and burns off in the tempering process.Preferred embodiments utilize an approximately 3-5 nm thick sputteredcarbon topcoat as the outermost layer. This material preferably is DCmagnetron sputtered in argon.

In a preferred embodiment, the invention provides a low-emissivitycoating on a substrate, the coating comprising, in order outward fromthe substrate a first dielectric layer having a thickness up to about 25nm, preferably up to about 23 nm; a first Ag layer having a thickness ofabout 8 nm to about 15 nm; a first absorbing barrier layer having athickness of about 0.1 nm to about 4 nm; a second dielectric layerhaving a thickness of about 40 nm to about 75 nm; a second Ag layerhaving a thickness of about 8 nm to about 15 nm; a second absorbingbarrier layer having a thickness of about 0.1 nm to about 4 nm; a thirddielectric layer having a thickness of about 10 nm to about 40 nm; andoptionally, a topcoat layer. In a further embodiment, the coatingcomprises a nucleation layer between the first dielectric layer and thefirst Ag layer, the nucleation layer having a thickness of about 4 nm toabout 12 nm. In a still further embodiment, the coating comprises asecond nucleation layer between the second dielectric layer and thesecond Ag layer, the second nucleation layer having a thickness of about2 nm to about 8 nm. A stack having a first dielectric layer with athickness of about 23 nm is particularly suitable for tempering.

In another preferred embodiment, the invention provides a low-emissivitycoating on a substrate, the coating comprising, in order outward fromthe substrate a first dielectric layer comprising SiAlOxNy; a firstnucleation layer comprising ZnAlOx; a first infrared reflecting layercomprising Ag; a first absorbing barrier layer comprising NiCr; a seconddielectric layer comprising SiAlOxNy; a second nucleation layercomprising ZnAlOx; a second infrared reflecting layer comprising Ag; asecond absorbing barrier layer comprising NiCr; a third dielectric layercomprising SiAlOxNy; and optionally, a topcoat layer. In alternateembodiments, the absorbing barrier layers comprise NiCrOx.

In another preferred embodiment, the invention provides a low-emissivitycoating on a substrate, the coating comprising, in order outward fromthe substrate a first dielectric layer comprising SiAlOxNy and having athickness up to about 25 nm, preferably up to about 23 nm; a firstnucleation layer comprising ZnAlOx and having a thickness of about 4 nmto about 12 nm; a first Ag layer having a thickness of about 8 nm toabout 15 nm; a first absorbing barrier layer comprising NiCr and havinga thickness of about 0.1 nm to about 4 nm; a second dielectric layercomprising SiAlOxNy and having a thickness of about 40 nm to about 80nm; a second nucleation layer comprising ZnAlOx and having a thicknessof about 2 nm to about 8 nm; a second Ag layer having a thickness ofabout 8 nm to about 15 nm; a second absorbing barrier layer comprisingNiCr and having a thickness of about 0.1 nm to about 4 nm; a thirddielectric layer comprising SiAlOxNy and having a thickness of about 10nm to about 40 nm; and optionally, a topcoat layer. In alternateembodiments, the absorbing barrier layers comprise NiCrOx. A stackhaving a first dielectric layer with a thickness of about 23 nm isparticularly suitable for tempering.

In an embodiment, the present invention provides a low-emissivitycoating on a substrate, the coating comprising, in order outward fromthe substrate a first dielectric layer comprising SiAl_(x)N_(y)O_(w) andhaving a thickness of about 3 nm to about 25 nm; a first nucleationlayer comprising ZnAlyOx and having a thickness of about 4 nm to about12 nm; a first Ag layer having a thickness of about 8 nm to about 12 nm;a first barrier layer comprising NiCrOx and having a thickness of about1 nm to about 4 nm; a first absorbing layer comprising NiCr and having athickness of about 1.5 nm to about 4 nm; a second dielectric layercomprising SiAl_(x)N_(y)O_(w) and having a thickness of about 55 nm toabout 75 nm; a second nucleation layer comprising ZnAlOx and having athickness of about 3 nm to about 10 nm; a second Ag layer having athickness of about 10 nm to about 15 nm; optionally, a second barrierlayer comprising NiCrOx and having a thickness of about 2 nm to about 4nm; a second absorbing layer comprising NiCr and having a thickness ofabout 0.7 nm to about 2.2 nm; a third dielectric layer comprisingSiAl_(x)N_(y)O_(w) and having a thickness of about 24 nm to about 40 nm;and optionally, a topcoat layer. In embodiments, the second barrierlayer comprising NiCrOx is absent, so that the second absorbing layer isdeposited directly on the second Ag layer. As an alternative to the NiCrmetal in the second absorbing layer in this described embodiment,co-sputtered NiCr and Chromium, a NiCr/Cr bilayer, or any absorbing graymetal or alloy may be used. Further alternatives include, withoutlimitation, a nichrome alloy comprising any Ni:Cr ratio, a NiCr layer inwhich the Ni:Cr ratio is graded, a NiCr layer reacted with nitrogen toform NiCrNx, and a dual layer optical absorber comprising NiCr/NiCr,wherein either metal may be any ratio of Ni and Cr.

In a further embodiment, the present invention provides, as illustratedin FIG. 9, for example, a low-emissivity coating on a substrate, thecoating comprising, in order outward from the substrate a firstdielectric layer; a first nucleation layer; a first Ag layer; a firstbarrier layer; a first optical absorbing layer; a second dielectriclayer; a second nucleation layer; a second Ag layer; a second opticalabsorbing layer; a third dielectric layer; and optionally, a topcoatlayer, preferably scratch resistant. Layer thicknesses are as describedherein. In an alternate embodiment, as illustrated in FIG. 10, forexample, the coating comprises, in order outward from the substrate,SiAlOxNy/ZnO/Ag/NiCrOx/NiCr metal/SiAlOxNy/ZnO/Ag/NiCrmetal/SiAlOxNy/optional topcoat. Therefore, in this embodiment, a secondNiCr metal absorbing layer is deposited directly on the second Ag layer.This embodiment may be tempered or heat strengthened without suchtempering or heat strengthening causing degradation in the stack layersor in the optical qualities of the coated substrate or causing the otherdrawbacks typically seen when such processes are used in connection withlow emissivity coatings. In addition to improved temperability, thisconfiguration (in which the second absorbing layer is directly depositedon the second Ag layer) exhibits improved mechanical durability. It hasbeen noted also that color appears to be easier to tune to preferredsetpoints with this embodiment. As an alternative to the NiCr metal inthe second absorbing layer, co-sputtered NiCr and Chromium, a NiCr/Crbilayer, or any absorbing gray metal, or alloy may be used. Furtheralternatives include, without limitation, a nichrome alloy comprisingany Ni:Cr ratio, a NiCr layer in which the Ni:Cr ratio is graded, a NiCrlayer reacted with nitrogen to form NiCrNx, and a dual layer opticalabsorber comprising NiCr/NiCr, wherein either metal may be any ratio ofNi and Cr.

The invention further provides low-emissivity stacks comprising at leastone absorbing layer (which, as described, can be a separate layer, or abarrier layer modified to have increased absorption properties), thelow-emissivity stack being characterized by a solar heat gaincoefficient (SHGC) that is less than about 0.34, preferably less thanabout 0.31, and, in some preferred embodiments, about 0.22 to about0.25. In embodiments, the stack includes a glass substrate having athickness of about ⅛ inch and exhibiting a light transmittance of about42% to about 46%. Embodiments also are provided which exhibit a lighttransmittance of about 50% to about 62%. In some embodiments, the stackhas a transmittance color with a negative a* and a negative b*. Inalternate embodiments, the stack has a transmittance color with anegative a* and a positive b*.

The invention further provides methods of making low-emissivity stackshaving a low SHGC as described, the methods including depositing on asubstrate the coatings described herein. The layers in the multilayercoatings of the present invention can be deposited by conventionalphysical and chemical vapor deposition techniques. The details of thesetechniques are well known in the art and will not be repeated here.Suitable deposition techniques include sputtering methods. Suitablesputtering methods include DC sputtering, using metallic targets, and ACand RF sputtering, using metallic and non-metallic targets. All canutilize magnetron sputtering. The sputtering can be in an inert gas, orcan be carried out reactively in reactive gas. The total gas pressurecan be maintained in a range from 5×10 ⁻⁴ to 8×10⁻² mbar, preferablyfrom 1×10⁻³ to 1×10⁻² mbar. Sputtering voltages can be in a range from200 to 1200 V, preferably 250 to 1000 V. Dynamic deposition rates can bein a range of from 25 to 4000 nm-mm²/W-sec, preferably 30 to 700nm-mm²/W-sec. Coaters manufactured by Leybold Systems GmbH with modelnumbers Typ A 2540 Z 5 H/13-22 and Typ A 2540 Z 5 H/20-29 are suitablefor sputter depositing the multilayer coatings of the present invention.

As indicated, the multiple layers of silver in the low emissivitycoating of the present invention provide greater efficiency inreflecting IR radiation, and a sharper cut-off between transmitted andreflected wavelengths, than is possible with a single layer of silver.

The multilayer coating of the present invention is deposited on and ismechanically supported by the substrate. The substrate surface serves asa template for the coating, and influences the surface topography of thecoating. To maximize transmission of visible light, preferably thesurface of the substrate has a roughness less than the wavelength of thelight. Such a smooth surface can be formed by, e.g., solidifying a meltof the substrate. The substrate can be any material having an emissivitythat can be lowered by the multilayer coating of the present invention.For architectural and automotive applications, the substrate ispreferably a material which has superior structural properties andminimum absorption in the visible and near-infrared spectra regionswhere the solar energy is concentrated. Crystalline quartz, fusedsilica, soda-lime silicate glass and plastics, e.g., polycarbonates andacrylates, are all preferred substrate materials.

As used in the present specification, the language “deposited onto” or“deposited on” means that the substance is directly or indirectlyapplied above the referenced layer. If applied indirectly, one or morelayers may intervene. Furthermore, unless otherwise indicated, indescribing coatings of the present invention by use of the format“[substance 1]/[substance 2]/[substance 3]/ . . . ” or the format “afirst [substance 1] layer; a first [substance 2] layer; a second[substance 1] layer; a second [substance 2] layer; . . . ”, or the like,it is meant that each successive substance is directly or indirectlydeposited onto the preceding substance.

Coated articles according to different embodiments of this invention maybe used in the context of architectural windows (e.g., IG units),automotive windows, or any other suitable application. Coated articlesdescribed herein may or may not be heat treated in different embodimentsof this invention. FIG. 5 depicts an embodiment of the inventionsuitable for use in an automotive or other vehicle application (such asa windshield or similar laminate). In the illustrated embodiment, acoating in accordance with the present invention is included in a stackwhich also comprises two glass substrates and a polyvinyl butyral (PVB)layer. The coating can be on the first sheet or the second sheet,provided it is facing the PVB.

Certain terms are prevalently used in the glass coating art,particularly when defining the properties and solar managementcharacteristics of coated glass. Such terms are used herein inaccordance with their well known meaning. For example, as used herein:

Intensity of reflected visible wavelength light, i.e. “reflectance” isdefined by its percentage and is reported as R_(x) Y or R_(x) (i.e. theRY value refers to photopic reflectance or in the case of TY photopictransmittance), wherein “X” is either “G” for glass side or “F” for filmside. “Glass side” (e.g. “G”) means, as viewed from the side of theglass substrate opposite that on which the coating resides, while “filmside” (i.e. “F”) means, as viewed from the side of the glass substrateon which the coating resides.

Color characteristics are measured and reported herein using the CIE LAB1976 a*, b* coordinates and scale (i.e. the CIE 1976 a*b* diagram, D6510 degree observer), wherein:

L* is (CIE 1976) lightness units

a* is (CIE 1976) red-green units

b* is (CIE 1976) yellow-blue units.

Other similar coordinates may be equivalently used such as by thesubscript “h” to signify the conventional use of the Hunter method (orunits) I11. C, 100 observer, or the CIE LUV u*v* coordinates. Thesescales are defined herein according to ASTM D-2244-93 “Standard TestMethod for Calculation of Color Differences From Instrumentally MeasuredColor Coordinates” Sep. 15, 1993 as augmented by ASTM E-308-95, AnnualBook of ASTM Standards, Vol. 06.01 “Standard Method for Computing theColors of Objects by 10 Using the CIE System” and/or as reported in IESLIGHTING HANDBOOK 1981 Reference Volume.

The terms “emissivity” (or emittance) and “transmittance” are wellunderstood in the art and are used herein according to their well knownmeaning. Thus, for example, the term “transmittance” herein means solartransmittance, which is made up of visible light transmittance (TY ofT_(vis)), infrared energy transmittance (T_(IR)), and ultraviolet lighttransmittance (T_(uv)) Total solar energy transmittance (TS orT_(solar)) can be characterized as a weighted average of these othervalues. With respect to these transmittances, visible transmittance maybe characterized for architectural purposes by the standard I11. D65 10degree technique; while visible transmittance may be characterized forautomotive purposes by the standard I11. A 2 degree technique (for thesetechniques, see for example ASTM E-308-95, incorporated herein byreference). For purposes of emissivity a particular infrared range (i.e.2,500-40,000 nm) is employed.

“Emissivity” (or emittance) (“E” or “e”) is a measure, or characteristicof both absorption and reflectance of light at given wavelengths. It isusually represented by the formula: E=1−Reflectance_(film). Forarchitectural purposes, emissivity values become quite important in theso-called “mid-range”, sometimes also called the “far range” of theinfrared spectrum, i.e. about 2,500-40,000 nm., for example, asspecified by the WINDOW 4.1 program, LBL-35298 (1994) by LawrenceBerkeley Laboratories, as referenced below. The term “emissivity” asused herein, is thus used to refer to emissivity values measured in thisinfrared range as specified by ASTM Standard E 1585-93 entitled“Standard Test Method for Measuring and Calculating Emittance ofArchitectural Flat Glass Products Using Radiometric Measurements”. ThisStandard, and its provisions, are incorporated herein by reference. Inthis Standard, emissivity is reported as hemispherical emissivity(E_(h)) and normal emissivity (E_(n)).

The actual accumulation of data for measurement of such emissivityvalues is conventional and may be done by using, for example, a BeckmanModel 4260 spectrophotometer with “VW” attachment (Beckman ScientificInst. Corp.). This spectrophotometer measures reflectance versuswavelength, and from this, emissivity is calculated using the aforesaidASTM Standard 1585-93.

The term Rsoiar refers to total solar energy reflectance (glass sideherein), and is a weighted average of IR reflectance, visiblereflectance, and UV reflectance. This term may be calculated inaccordance with the known DIN 410 and ISO 13837 (December 1998) Table 1,p. 22 for automotive applications, and the known ASHRAE 142 standard forarchitectural applications, both of which are incorporated herein byreference.

“Haze” is defined as follows. Light diffused in many directions causes aloss in contrast. The term “haze” is defined herein in accordance withASTM D 1003 which defines haze as that percentage of light which inpassing through deviates from the incident beam greater than 2.5 degreeson the average. “Haze” may be measured herein by a Byk Gardner hazemeter (all haze values herein are measured by such a haze meter and aregiven as a percentage of light scattered). Another term employed hereinis “sheet resistance”. Sheet resistance (R_(s)) is a well known term inthe art and is used herein in accordance with its well known meaning. Itis here reported in ohms per square units. Generally speaking, this termrefers to the resistance in ohms for any square of a layer system on aglass substrate to an electric current passed through the layer system.Sheet resistance is an indication of how well the layer or layer systemis reflecting infrared energy, and is thus often used along withemissivity as a measure of this characteristic. “Sheet resistance” mayfor example be conveniently measured by using a 4-point probe ohmmeter,such as a dispensable 4-point resistivity probe with a MagnetronInstruments Corp. head, Model M-800 produced by Signatone Corp. of SantaClara, Calif.

“Chemical durability” or “chemically durable” is used hereinsynonymously with the term of art “chemically resistant” or “chemicalstability”. Chemical durability is determined by an immersion testwherein a 2″×5″ or 2″×2″ sample of a coated glass substrate is immersedin about 500 ml of a solution containing 4.05% NaCl and 1.5% H₂O₂ for 20minutes at about 36° C. Chemical durability can also be determined bythe Cleveland test or the climatic chamber test, as follows.

Cleveland Chamber Set Up

Samples are cut down to 4″×12″ or 6″×12″ for this test. The water isheated to 50° C.±2° C. and the room temperature kept at 23° C.±3° C.(73° F.±5° F.). Samples are placed film side down over the heated waterbath. Within a few minutes of exposure the samples are covered with athick layer of condensed water. As time progresses, the water drips downthe face of the sample and new condensation forms on the sample.Condensed water is present on the samples for the entire duration of thetest.

Climatic Chamber Set Up

Samples are cut down to 4″×6″ for this test. For the static humiditytest, humidity is held a 98% relative humidity (RH) while thetemperature cycles between 45° and 55° C. in one hour.

Measurements Performed

Samples are removed after 1, 3, and 7 days of exposure for measurements.Haze, emissivity, and film side reflection are measured.

To calculate delta haze:

Delta Haze=Post-Test Haze−Pre-Test Haze

To calculate delta E:

-   Delta E=(delta L*̂2+delta a*̂2+delta b*̂2)̂½, where the delta L, a*, and    b* are pre-test minus post-test measurements.

To calculate percent change in emissivity use this formula:

Change in emissivity=(E post-test−E pre-test)/(Eglass−Epre-test).

“Scratch durabilility,” as used herein is defined by the following test.The test uses a Erichsen Model 494 brush tester and Scotch Brite 7448abrasive (made from SiC grit adhered to fibers of a rectangular pad)wherein a standard weight brush or a modified brush holder is used tohold the abrasive against the sample. 100-500 dry or wet strokes aremade using the brush or brush holder. Damage caused by scratching can bemeasured in three ways: variation of emissivity, haze and E for filmside reflectance. This test can be combined with the immersion test orheat treatment to make the scratches more visible. Good results can beproduced using 200 dry strokes with a 135 g load on the sample. Thenumber of strokes could be decreased or a less aggressive abrasive couldbe used if necessary. This is one of the advantages of this test,depending on the level of discrimination needed between the samples, theload and/or the number of strokes can be adjusted. A more aggressivetest could be run for better ranking. The repeatability of the test canbe checked by running multiple samples of the same film over a specifiedperiod.

The terms “heat treatment”, “heat treated” and “heat treating” as usedherein mean heating the article to a temperature sufficient to enablethermal tempering, bending, or heat strengthening of the glass inclusivearticle. This definition includes, for example, heating a coated articleto a temperature of at least about 1100 degrees F. (e.g., to atemperature of from about 550 degrees C. to 700 degrees C.) for asufficient period to enable tempering, heat strengthening, or bending.

The term “Solar Heat Gain Coefficient (or SHGC)” (“g”) is well known inthe art and refers to a measure of the total solar heat gain through awindow system relative to the incident solar radiation.

Unless otherwise indicated, the additional terms listed below areintended to have the following meanings in this specification.

-   Ag silver-   TiO₂ titanium dioxide-   NiCrO_(x) an alloy or mixture containing nickel oxide and chromium    oxide. Oxidation states may vary from stoichiometric to    substoichiometric.-   NiCr an alloy or mixture containing nickel and chromium.-   SiAlN_(x) or SiN_(x) reactively sputtered silicon aluminum nitride.    Sputtering target typically contains 1-20 weight % Al. The    sputtering gas is a mixture of Ar, N₂, and O₂. Dependant on the gas    mixture and the sputtering power, the material is more or less    absorbing.-   SiAlN_(x)O_(y) or SiN_(x)O_(y) reactively sputtered silicon aluminum    oxy-nitride. Sputtering target typically contains 1-20 weight % Al.    The sputtering gas typically is a mixture of Ar, N₂ and O₂.    Dependant on the gas mixture and the sputtering power, the material    is more or less absorbing.

ZnAl_(y)O_(x) reactively sputtered Zn aluminum oxide. Sputtering targettypically contains 1-20 weight % Al. The sputtering gas is a mixture ofAr and O₂.

-   Zn_(x)Sn_(y)Al_(z)O_(w) reactively sputtered zinc tin (aluminum)    oxide. Sputtering target typically a zinc tin alloy with optional Al    doping. The zinc tin alloy covers a wide range from zinc rich to tin    rich alloys. The sputtering gas is a mixture of Ar and O₂.-   Zr zirconium-   optical coating one or more coatings applied to a substrate which    together affect the optical properties of the substrate-   low-e stack transparent substrate with a low heat emissivity optical    coating consisting of one or more layers-   barrier layer deposited to protect another layer during processing,    especially a heat reflecting silver layer. May provide better    adhesion of upper layers, may or may not be present after    processing.-   layer a thickness of material having a function and chemical    composition bounded on each side by an interface with another    thickness of material having a different function and/or chemical    composition. Deposited layers may or may not be present after    processing due to reactions during processing. “Layer”, as used    herein, encompasses a thickness of material that may be bounded on a    side by air or the atmosphere (such as, for example, the top layer    or protective overcoat layer in a coating stack or surmounting the    other layers in the stack).-   co-sputtering Simultaneous sputtering onto a substrate from two or    more separate sputtering targets of two or more different materials.    The resulting deposited coating may consist of a reaction product of    the different materials, an un-reacted mixture of the two target    materials or both.-   Intermetallic A certain phase in an alloy system composed of    specific stoichiometric-   compound    -   proportions of two or more metallic elements. The metal elements        are electron or interstitial bonded rather existing in a solid        solution typical of standard alloys. Intermetallics often have        distinctly different properties from the elemental constituents        particularly increased hardness or brittleness. The increased        hardness contributes to their superior scratch resistance over        most standard metals or metal alloys.-   Mechanical-   Durability This term refers (unless otherwise noted) to a wet brush    durability test carried out on an Erichsen brush tester (Model 494)    using a nylon brush (Order number 0068.02.32. The brush weighs 450    grams. The individual bristle diameter is 0.3 mm. Bristles are    arranged in groups with a diameter of 4 mm). The test is run for    1000 strokes (where one stroke is equal to a full cycle of one back    and for motion of the brush). The samples are brushed on the coated    side and submerged in de-ionized water during the brushing    procedure.

In various embodiments, the low emissivity stacks of the presentinvention exhibit the following independent characteristics: transmittedY of about 30 to about 62, preferably about 35 to about 55 and mostpreferably about 40 to about 50; an transmitted a* value which isnegative, most preferably about −1 to about −6; preferably a b* valuewhich is negative, most preferably about 0 to about −6; RgY of about 8to about 20, more preferably about 10 to about 18, most preferably about11 to about 17; Rga* which is negative, most preferably about −1 toabout −7; preferably an Rgb* value that is negative, most preferably −1to about −7; RfY between about 2 and about 12, more preferably about 2to about 10, and most preferably about 2 to about 8; Rfa* which isnegative, most preferably about −2 to about −20; preferably an Rfb* ofabout −10 to about +10, most preferably about −6 to about +6; and a SHGCof about 0.10 to 0.30, up to about 0.34, more preferably about 0.15 toabout 0.28, most preferably about 0.20 to about 0.25.

To further illustrate the invention, the following non-limiting examplesare also provided:

EXAMPLE 1

In the present example, depicted in FIG. 4, a low-e coating is depositedon a glass substrate to form a stack having the following configuration:Glass/12 nm oxide/10 nm Ag/2 nm NiCrOx/4 nm NiCr/72 nm oxide/13 nm Ag/2nm NiCrOx/3 nm NiCr/23 nm oxide/7 nm SiN. The oxide can be sputteredfrom a Ti, Zn, Sn, ZnSn alloy, or Bi target The oxide may compriseNb₂O₅. The oxide may comprise up to about 20 wt %, preferably up toabout 10 wt % of an element, such as Al or B, or similar such element tomake the coater target conductive. The SiN topcoat is optional. Thisexemplified coating has an appealing transmittance color with a* and b*negative. The SHGC is below 0.30. The coating has an acceptablemechanical and chemical durability.

EXAMPLE 2

In the present example, a low-e coating is deposited on a glasssubstrate to form a stack having the following configuration: about ⅛inch Glass/0-15 nm dielectric/2-10 nm nucleation layer/8-15 nmAg/0.1-4nm barrier/0.2-8 nm Absorbing layer/40-75 nm dielectric/2-10 nmnucleation layer/8-18 nmAg/0.1-4 nm barrier/0.2-8 nm Absorbinglayer/10-40 nm dielectric/topcoat. The dielectric can be an oxide (as inexample 1) or a nitride or an oxy-nitride of Si, SiAl, SiB, SiZr and itmay contain up to about 20 wt %, preferably up to about 10 wt % of anelement, such as Al and B, to make the coater target conductive. Thenucleation layer improves the properties of the Ag layer and istypically based on Zn oxide with up to 15 wt % of other elements such asAl, Sn or a combination thereof.

The barrier protects the Ag against the attack of the plasma whensputtering the dielectric atop. It also improves the chemical durabilityby controlling the diffusion of aggressive species such as O₂, O, H₂O,and Na+. Suitable barriers include, without limitation, NiCr, NiCrOx,NiCrNxOy, TiOx, Ti and other metals.

As indicated, the topcoat is optional. When included, it can have apositive impact on the chemical and mechanical stability. A suitabletopcoat includes but is not limited to C, ZrSi, or silicides. Typically,the topcoat has a contrasting nature compared to the underlyingdielectric. If the dielectric is an oxide, the topcoat will be one ofthe materials described above or a nitride or an oxy-nitride (forinstance SiN or SixAlyNzOc). In the alternative, when the dielectric isa nitride or an oxynitride, the top coat can advantageously be an oxide,such as, without limitation, ZrO₂, ZrSiO₂, SnO₂, ZrOxNy, or TiO₂.

EXAMPLE 3

In the present example, a low-e coating is deposited on a glasssubstrate to form a stack having the following configuration: about ⅛inch Glass/3-15 nm SiAlxNyOw/3-10 nm ZnAlyOx/8-12 nm Ag/1-4 nmNiCrOx/1.5-3.0 nm NiCr/55-65 nm SiAlxNyOw/3-10 nm ZnAlyOx/10-15 nmAg/1-4 nm NiCrOx/0.7-2.2 nm NiCr/24-32 nm SiAlxNyOw/optional top coat.The top coat, if included, can be chosen from, but is not limited to 1-5nm C, 1-10 nm of ZrO₂, or ZrSiO₂. The coating in the present exampleexhibits a light transmittance of about 42% to about 46%, as measured onan IGU, a SHGC below about 0.30, and the transmittance color is gray andcan be adjusted for a green to a blue hue. The IGU includes ⅛″ coatedglass, with the coating in position 2, and ⅛″ clear class, with a ½″gap. The coating has improved chemical and mechanical durability. Thedouble layer NiCrOx/NiCr in this example has a positive impact inachieving the sought after properties. Because of the specific locationof the NiCr, the coating can be produced on an existing coater that isprimarily dedicated to low-e coating. It does not require specificisolation of the NiCr sputtering target. A summary of the propertiesobserved in the above exemplified stacks is provided in the table below:

Example 1 Example 2 Example 3 Aesthetics neutral neutral neutral SHGCbelow .30 below .30 below .30 Aesthetics good good good Angularstability good good good Humidity resitance good good good Chemicaldurability good good good Mechanical durability good good good

EXAMPLE 4

The present Example represents a preferred non-tempered coating, withthickness data, in accordance with the invention. Thicknesses weremeasured with a DekTak Profilometer. In measuring the thicknesses, aninitial thickness measurement was made on the entire stack.Subsequently, the top layer was turned off in the coater and thethickness of the stack minus the top SiAlOyNx layer was measured. Thiswas repeated with layers turned off one at a time, until lastly, thebottom SiAlOyNx alone was measured. The accuracy of the measurements isapproximately ±0.5 nm.

Individual layer LAYER thickness (nm) top SiAlOxNy 33.4 top NiCr 0.5 Ag13.5 ZnAlOx 6.2 mid SiAlOxNy 68.2 bot NiCr 3.0 NiCrOx 1.3 Ag 10.6 ZnAlOx9.0 bot SiAlOxNy 23.0

EXAMPLE 5

The present Example represents a preferred temperable coating, whichincludes a carbon topcoat, in accordance with embodiments of theinvention. Thicknesses were measured with a Dektak Profilometer as inExample 4 above. In these measurements, the top SiAlOxNy and carbontopcoat thicknesses were not separated. The carbon is estimated to beapproximately 5 nm thick, thereby making the top SiAlOxNy layerapproximately 33 nm.

Individual layer LAYER thickness (nm) top SiAlOxNy 38.6 and carbontopcoat top NiCr 0.1 Ag 13.2 ZnAlOx 9.4 mid SiAlOxNy 67.4 bot NiCr 3.6NiCrOx 1.0 Ag 9.8 ZnAlOx 10.7 bot SiAlOxNy 23.3

EXAMPLE 6

The table below represents optical and electrical measurements taken ofcoatings in accordance with embodiments of the invention. The “low-g A”product is an annealed product on which no heat treatment was carriedout. The “low-g T” product is a temperable product, which includes atopcoat in accordance with the invention. “BB” represents measurementstaken before tempering and “AB” represents measurements taken aftertempering. “N/A” indicates no measurements were obtained duringgeneration of this particular example.

low-g A (no heat treatment done) low-g T BB only BB AB Transmitted Y(monolithic on ⅛″ glass) 44.7 42.9 45.37 a*t (transmissive): (monolithicon ⅛″ glass) −5.1 −.51 5.3 b*t (transmissive): (monolithic on ⅛″ glass)−4.3 1.59 −4.3 RtY (outside reflectance): (monolithic on ⅛″ glass) 11.511.4 11.9 a*g (outside reflective): (monolithic on ⅛″ glass) −1.7 −4.8−2.7 b*g (outside reflective): (monolithic on ⅛″ glass) −4.2 −6.7 −4.6SHGC: (in IGU) 0.23 N/A N/A SC 0.26 N/A N/A T_(ultraviolet) 0.178 N/AN/A Rs 2.3 2.3 1.9 Transmitted ΔE* (delta L*a*b*) (monolithic on ⅛″glass) 12.1 Glass side reflection ΔE* (delta L*a*b*) (monolithic on ⅛″3.1 glass)

EXAMPLE 7

The present Example represents a summary of the specifications ofvarious coatings in accordance with the present invention. Optical andelectrical properties of non-tempered and temperable coatings inaccordance with certain embodiments of the invention would fall withinthe specifications set forth in the table below.

Normal Incidence Color Specification for low-g coatings TransmissionGlass Side R Film Side R TY a* b* RGY a* b* RFY a* b* NC Rs SHGC Min42.0 −6.0 −4.5 10.0 −3.0 −3.0 2.0 −18.0 −4.0 2.0 0.22 Max 46.0 −3.0 −1.512.0 −1.0 −6.0 6.0 −10.0 4.0 2.4 0.25

EXAMPLE 8

The present Example represents a substrate having a coating inaccordance with the invention. As noted, an optional carbon topcoat (notdepicted) can be employed in embodiments intended to be subjected totempering or heat treatment and is preferably about 3 nm to about 5 nmin thickness. The optional topcoat is preferably not included inembodiments not intended to be tempered or heat treated. Suchembodiments are referred to herein as “annealed.” Layer thicknesses forthe exemplified embodiment shown below are approximate. Accuracy withrespect to the dielectric and Ag layers is in the range of about ±20%.The thickness of the NiCr layers can be plus 200% minus 20%. In annealedcoatings, the ZnAlOx layers typically are thinner and may be as low as60% of the values noted in the table below.

Individual layer LAYER thickness (nm) top SiAlOxNy 31 top NiCr 1.6 Ag11.4 ZnAlOx 8.4 mid SiAlOxNy 79.7 bot NiCr 1.1 Ag 11.2 ZnAlOx 7.7 botSiAlOxNy 24.2 Substrate

The descriptions of the materials noted in the table are as follows:

-   SiAlOxNy—In embodiments represented by the present example, this    material is reactively sputtered from a silicon/10 weight percent    aluminum rotatable cathode. The reactive gas is about 90% nitrogen    flow and 10% oxygen. This material is used for the bottom, middle,    and top primary dielectric layers. Although stoichiometry variations    can occur from layer to layer and from production run to production    run, all of the SiAlOxNy in the present example is    sub-stoichiometric. Insufficient nitrogen and oxygen are present in    the sputtering gas for the SiAl to reach a fully reacted    oxy-nitride. Atomic ratios in the layer are approximately    Si₄O_(0.4)N₅.-   ZnAlOx—In embodiments represented by the present example, this    material is reactively sputtered from a zinc/1.5 weight percent    aluminum rotatable or planar cathode. The sputtering gas consists of    argon and sufficient oxygen for the oxide to be deposited in a fully    oxidized state. This layer serves as a nucleation layer for the    silver and is consistent with such layers commonly described in    low-e patent literature.-   Ag—In embodiments represented by the present example, the silver    layers may be sputtered in pure argon or, alternatively, a small    amount of oxygen may be added. The oxygen helps with mechanical    durability in the tempered version, but is not always necessary.-   NiCr—In embodiments represented by the present example, this thin,    protective or barrier layer sputtered on silver is deposited from DC    planar targets and is sputtered in argon only. In this example,    these layers are fully metallic except for unintentional impurities    such as gas crosstalk from neighboring cathodes.-   Carbon—Temperable versions of the exemplified embodiment utilize a    3-5 nm thick sputtered carbon topcoat as the outermost layer, which    is DC magnetron sputtered in argon.

In the present example, gas distributions for all materials aresymmetric in the machine direction. In the across machine direction, gasflows for reactive materials may be varied for tuning cross-machineuniformity.

It is preferable in the various embodiments described herein that thetop Ag layer be thicker than the bottom Ag layer and the bottomabsorbing barrier layer be thicker than the top absorbing barrier layer.(In the present example, the absorbing barrier layers are NiCr, but, asnoted, alternate embodiments employ NiCrOx for such layers.) Suchreverse thickness ratios are advantageous in achieving preferred colorsof the stack. It is also preferable that the bottom dielectric layer(SiAlOxNy in the present example) be thicker than the middle and topdielectric layers. Such a configuration similarly is advantageous inachieving preferred colors. Furthermore, it is preferable that thebottom nucleation layer (ZnAlOx in the present example) be thicker thanthe top nucleation layer. Such a configuration provides for improvedmechanical and chemical durability. In preferred embodiments, the stacklayer ratios fall generally into the following ranges:

-   bottom Ag/top Ag: about 0.8 to about 1.0-   bottom NiCr/top NiCr: about 1.2 to about 2.0-   bottom ZnAlOx/top ZnAlOx: About 1.2 to about 2.0-   bottom SiAlOxNy/top SiAlOxNy: about 0.4 to about 0.8-   middle SiAlOxNy/top SiAlOxNy: about 1.5 to about 2.5.

It is further advantageous for the top dielectric to have a lower indexof refraction than either the bottom or middle dielectric. Preferredranges include:

-   top index: about 1.8 to about 2.3;-   bottom or middle: about 2.0 to about 2.5.

The present Example exhibits the following color and solar performance.

Normal Incidence Color Specification for monolithic LowG on ⅛″ glassReflection Reflection Transmission (uncoated side) (coated Side) LowG ATY a* b* RGY a* b* RFY a* b* NC Rs SHGC Min 42.0 −6.0 −4.5 12.0 −3.0−3.0 2.0 −12.0 −4.0 2.0 0.22 Max 46.0 −3.0 −1.5 16.0 −1.0 −6.0 6.0 −4.02.0 2.4 0.25 “NC Rs” refers to noncontact surface resistance and themeasurement is in units of ohms/square.In tempered embodiments, tempering color shift, or ΔE, is greater than 3for the glass side reflection color. This is due to the burning off ofthe carbon layer.

EXAMPLE 9

Annealed Stack Material (in nm) Temperable Stack (in nm) Carbon n/a 0.14Top SiAlOxNy 36.4 36.2 Top NiCrOx 5.7 4.7 Top Ag 10.2 11.6 Top ZnAlOx6.5 5.3 Middle SiAlOxNy 71.0 71.1 Bottom NiCrOx 2.4 5.2 Bottom Ag 14.814.1 Bottom ZnAlOx 3.9 16.5 Bottom SiAlOxNy 22.4 24.3 Glass Substrate 3mm 3 mm

The present Example represents a substrate having a coating inaccordance with the invention. As noted, an optional carbon topcoat (notdepicted) can be employed in embodiments intended to be subjected totempering or heat treatment and is preferably about 3 nm to about 5 nmin thickness. The optional topcoat is preferably not included inembodiments not intended to be tempered or heat treated. Suchembodiments are referred to herein as “annealed.” Layer thicknesses forthe embodiment shown in the table below are approximate.

With respect to the exemplified embodiment, thickness measurements weremade using a Dektak Profilometer. Slides with ink lines were coated withthe full stack to achieve the total stack thickness. Additional sampleswere prepared by turning off the upper most material cathodes one layerat a time until only the bottom SiAlOxNy was present. The ink lines wereremoved with Isopropyl Alcohol and the resulting steps were measuredwith the Dek Tak. Individual layer thicknesses were calculated bysubtracting the thickness of the remaining stack underneath. Thereforethe accuracy of the individual layers is affected by the accuracy of thelayers underneath them. The accuracy of the dielectrics (SiAlOxNy) andthe silvers (Ag) is in the range of ±20%. The thickness range of theNiCrOx layer is ±100%. Annealed embodiments in accordance with theinventions tend to have thinner bottom ZnAlOx than temperable versions.

The descriptions of the materials noted in the exemplified embodimentare as follows:

-   SiAlOxNy—In embodiments represented by the present example, this    material is reactively sputtered from a silicon/10 weight percent    aluminum rotatable cathode. The reactive gas is about 90% nitrogen    flow and 10% oxygen. This material is used for the bottom, middle,    and top primary dielectric layers.-   ZnAlOx—In embodiments represented by the present example, this    material is reactively sputtered from a zinc/1.5 weight percent    aluminum rotatable or planar cathode. The sputtering gas consists of    argon and sufficient oxygen for the oxide to be deposited in a fully    oxidized state. This layer serves as a nucleation layer for the    silver and is consistent with such layers commonly described in    low-e patent literature.-   Ag—In embodiments represented by the present example, the silver    layers may be sputtered in pure argon or, as an alternative, a small    amount of oxygen may be added. The oxygen helps with mechanical    durability in the tempered version.-   NiCrOx—In embodiments represented by the present example, this thin,    protective or barrier layer sputtered on silver is deposited from    planar targets and is sputtered in an argon oxygen mixture. The    power to oxygen flow (sccm) is the method used to estimate oxidation    in sputtered NiCrOx. The ratio used for fully oxidized NiCrOx is    10:1. The ratio used in preferred coatings in accordance with the    presently exemplified embodiment varies from 7.5:1 to 8.0:1.-   Carbon—Temperable versions of the exemplified embodiment utilize a    3-5 nm thick sputtered carbon topcoat as the outermost layer. This    material is DC magnetron sputtered in argon.

In the present example, gas distributions for all materials aresymmetric in the machine direction. In the across machine direction, gasflows for reactive materials may be varied for tuning cross-machineuniformity.

The present Example exhibits the following optical characteristics:

Annealed Temperable Optical Properties Monolithic IGU Monolithic IGUTvis 65.5% 59.8% 69.3% 63.1% a*t −3.29 −3.73 −1.13 −1.87 b*t 3.67 3.661.95 2.08 Outside Reflection 11.0% 14.4% 12.2% 15.9% (glass side) a*g−1.56 −2.06 −1.48 −1.49 b*g −7.41 −5.36 −3.56 −2.31 Inside Reflection5.7% 12.4% 8.9% 15.0% (film side) a*f −13.3 −6.09 −15.9 −9.09 b*f 1.361.13 2.92 2.28 SHGC 0.346 0.305 0.371 0.329 SC 0.40 0.35 0.43 0.38 Tuv0.27 0.23 0.30 0.25The present Example exhibits the following color and solar performance:

Mid G T Y a*t b*t Rg Y a*g b*g Rf Y a*f b*f NS Rs SHGC Min 63% −4 0 10%−4 −7 5% −16 0 1.5 0.25 Max 67% 0 4 12% −1 −3 9% −8 8 2.5 0.32 “NC Rs”refers to noncontact surface resistance and the measurement is in unitsof ohms/square.In tempered embodiments, ΔE is as follows:

6 color units for transmission.

10 color units for glass side reflection.

14 color units for film side reflection.

The color shift is due to the burning off of the carbon layer.

EXAMPLE 10

The present Example includes a coating having the following structure,which employs a 2:1 oxygen:kw ratio in the NiCr layer.

LAYER top SiAlOxNy top NiCr Ag ZnAlOx mid SiAlOxNy bot NiCr Ag ZnAlOxbot SiAlOxNy SubstrateProcess run data is provided in the table below:

Coater Set Up Temperable with 2:1 NiCrOx Reactive Voltage I P Ar O2 N2Gas:kW Cathode Target (V) (amp) (kW) (sccm) (sccm) (sccm) Pressure(×10⁻³ hPA) ratio  1 SiAl 425.9 194.1 51.9 300 30 344 3.66 6.63  2 SiAl601.3 149.7 51.9 300 30 344 4.22 6.63  5 ZnAl 431.1 179.3 39.3 150 420 02.65 0.00  7 ZnAl 328.7 178.4 39.4 150 420 0 1.88 10.66 10 Ag 436.3 29.813 100 20 0 1.12 1.54 20 NiCr 531.8 73.2 39 300 76.4 0 1.96  4 SiAl604.2 193.5 67.8 300 35 482 1.29 7.11 12 SiAl 615.2 208.3 68.3 300 30482 4.87 7.06 13 SiAl 581 202.1 68 300 30 482 4.25 7.09 15 SiAl 540.5212.3 67.7 300 30 482 7.12 17 SiAl 549.8 207.5 67.8 300 30 482 4.45 7.1117A SiAl 505.8 213.7 67.5 300 30 482 4.59 7.14 21 ZnAl 392.9 133.3 39.5150 500 0 1.66 0.00 23 Ag 565.4 14.6 8.2 100 20 0 1.62 0.00 19 NiCr536.2 31.8 17.1 300 35.6 0 1.56 2.08 26 SiAl 471.6 130.7 35.1 300 30 2540.85 27 SiAl 500.6 118.6 35.3 300 30 254 0.85 28 SiAl 484.4 121.9 35.2300 30 254 4.58 7.22 30 SiAl 560.8 128.2 35.4 300 30 254 7.18 18 C 519.1133.4 34.2 500 0 0 2.93 0.00

EXAMPLE 11

In the present Example, an annealed version of a coating in accordancewith the invention is provided. Description of the stack configurationand characteristics are included in the tables below. In the exemplifiedembodiment, absorbing barrier layers comprising NiCrOx are employed.

Material Thicknesses (in nm) Preferred More Annealed Layer RangePreferred Example −40% +40% Bottom SiN 13 to 31 nm 18 to 27 nm 22.38 1331 Bottom ZnOx 2 to 5 nm 3 to 5 nm 3.92 2 5 Bottom Ag 9 to 21 nm 12 to18 nm 14.76 9 21 Bottom NiCrOx 1 to 3 nm 2 to 3 nm 2.42 1 3 Middle SiN43 to 99 nm 57 to 85 nm 70.98 43 99 Top ZnOx 4 to 9 nm 5 to 8 nm 6.52 49 Top Ag 6 to 14 nm 8 to 12 nm 10.20 6 14 Top NiCrOx 3 to 8 nm 5 to 7 nm5.68 3 8 Top SiN 22 to 51 nm 29 to 44 nm 36.42 22 51 Low-ECharacteristics Characteristic General More Preferred Most Preferred Rs(ohms/sq) </=5.0 </=2.0 </=1.5 En </=0.07 </=0.04 </=0.03 MonolithicSolar Characteristics Characteristic General More Preferred example T Y(D65, 10°) >/=64% >/=66% 65.5% a*_(t) (D65, 10°) −10 to 0.0  −4.0 to−2.0 −3.29 b*_(t) (D65, 10°)   0 to 4.0 2.0 to 4.0 3.67 Rg Y (D65, 10°) 4% to 14% 10% to 12%   11% a*_(g) (D65, 10°) −10 to 0.0  −4.0 to −1.0−1.56 b*_(g) (D65, 10°) −10 to 0.0  −7.0 to −3.0 −7.41 Rf Y (D65, 10°) 4% to 14% 5% to 9%  5.7% a*_(f) (D65, 10°) −20 to 0.0   −16 to −8.0−13.3 b*_(f) (D65, 10°) 0.0 to 10  0.0 to 8.0 1.36 SHGC </=0.40 </=0.350.346 SC </=0.49 </=0.46 0.40 Tuv </=0.35 </=0.30 0.27 Tuv DamageWeighted </=0.49 </=0.46 0.514 (ISO) IGU Solar CharacteristicsCharacteristic General More Preferred Example T Y (D65,10°) >/=58% >/=60% 59.8% a*_(t) (D65, 10°) −10 to 0.0  −4.0 to −2.0−3.73 b*_(t) (D65, 10°)   0 to 4.0 2.0 to 4.0 3.66 Rg Y (D65, 10°)  4%to 20% 10% to 15% 14.4% a*_(g) (D65, 10°) −10 to 0.0  −4.0 to −1.0 −2.06b*_(g) (D65, 10°) −10 to 0.0  −7.0 to −3.0 −5.36 Rf Y (D65, 10°)  4% to20% 10% to 15% 12.4% a*_(f) (D65, 10°) −20 to 0.0   −16 to −8.0 −6.09b*_(f) (D65, 10°) 0.0 to 10  0.0 to 8.0 1.33 SHGC </=0.35 </=0.30 0.305SC </=0.43 </=0.40 0.35 U-value  0.20 to 0.30 0.22 to 0.25 0.24 Tuv</=0.30 </=0.25 0.23 Tuv Damage Weighted </=0.49 </=0.46 0.464 (ISO)

Example Coater Set Up Annealed Test #24 I P Ar O2 N2 Reactive CathodeTarget Voltage (V) (amp) (kW) (sccm) (sccm) (sccm) Pressure (×10−³ hPA)Gas:kW  1 SiAl 537.6 197.9 55.1 300 30 358 3.28 6.50  2 SiAl 494.2 206.655 300 30 358 3.44 6.51  6 SiAl 511.6 231.7 55.7 300 30 358 3.09 6.43  5ZnAl 448.5 111.4 29.3 150 350 0 1.61 11.95  9 Ag 526 52.1 27.5 100 0 0 ?0.00 20 NiCr 574.7 41.4 23.8 100 185 0 ? 7.77 11 SiAl 656.8 222.8 66.7300 30 405 3.37 6.07  4 SiAl 495.9 247.1 66.1 300 35 405 2.93 6.13 12SiAl 671.3 212.7 66.4 300 30 405 5.25 6.10 13 SiAl 579.9 217.5 66.1 30030 405 4.74 6.13 14 SiAl 474 255.9 66 300 30 405 4.24 6.14 15 SiAl 531.8222.6 65.9 300 30 405 1.03 6.15 16 SiAl 480.3 209.9 65.9 300 30 405 4.296.15 17 SiAl 583.3 211.8 65.9 300 30 405 4.57 6.15 17A SiAl 545.7 229.165.8 300 30 405 4.43 6.16 18A ZnAl 361.1 147.6 29.8 150 390 0 1.18 13.0922 Ag 667.2 26.2 17.5 100 0 0 ? 0.00 19 NiCr 612.6 38.1 23.3 100 192 0 ?8.24 25 SiAl 483.8 194.3 47.7 300 30 339 1.72 7.11 26 SiAl 443.9 195.847.9 300 30 339 4.99 7.08 27 SiAl 489 177.5 48 300 30 339 2.03 7.06 28SiAl 384.3 186 47.8 300 30 339 5.1 7.09 29 SiAl 479.7 185.2 47.9 300 30339 5.66 7.08 30 SiAl 524.9 177.7 48 300 30 339 3.83 7.06

Sample Monolithic &IGU #505 AC31 Annealed Solar CharacteristicsCharacteristic Monolithic IGU T Y (D65, 10°) 65.5% 59.8% a*_(t) (D65,10°) −3.29 −3.73 b*_(t) (D65, 10°) 3.67 3.66 Rg Y (D65, 10°)   11% 14.4%a*_(g) (D65, 10°) −1.56 −2.06 b*_(g) (D65, 10°) −7.41 −5.36 Rf Y (D65,10°)  5.7% 12.4% a*_(f) (D65, 10°) −13.3 −6.09 b*_(f) (D65, 10°) 1.361.33 SHGC 0.346 0.305 SC 0.40 0.35 Tuv 0.27 0.23 Tuv Damage Weighted0.514 0.464 (ISO)

EXAMPLE 12

In the present Example, a temperable version of a coating in accordancewith the invention is provided. Description of the stack configurationand characteristics are included in the tables below. In the exemplifiedembodiment, absorbing barrier layers comprising NiCrOx are employed.

Material Thicknesses (in nm) Preferred More Temperable Layer RangePreferred Example −40% +40% Bottom SiN 15 to 34 nm 19 to 29 nm 24.32 1534 Bottom 10 to 23 nm 13 to 20 nm 16.50 10 23 ZnOx Bottom Ag 8 to 20 nm11 to 17 nm 14.06 8 20 Bottom 3 to 7 nm 4 to 6 nm 5.24 3 7 NiCrOx MiddleSiN 43 to 100 nm 57 to 85 nm 71.10 43 100 Top ZnOx 3 to 7 nm 4 to 6 nm5.34 3 7 Top Ag 7 to 16 nm 9 to 14 nm 11.60 7 16 Top NiCrOx 3 to 7 nm 4to 6 nm 4.74 3 7 Top SiN 22 to 51 nm 29 to 43 nm 36.24 22 51 Top Carbon1 to 10 nm 3 to 5 nm 0.14 0 0 Low-E Characteristics More MostCharacteristic General Preferred Preferred Rs (ohms/sq) </=5.0 </=2.0</=1.5 En </=0.07 </=0.04 </=0.03 More Characteristic General PreferredMonolithic Solar Characteristics T Y (D65, 10°) >/=64% >/=66% 69.3%a*_(t) (D65, 10°) −10 to 0.0  −4.0 to −2.0 −1.13 b*_(t) (D65, 10°)   0to 4.0 2.0 to 4.0 1.95 Rg Y (D65, 10°)  4% to 14% 10% to 12% 12.2%a*_(g) (D65, 10°) −10 to 0.0  −4.0 to −1.0 −1.48 b*_(g) (D65, 10°) −10to 0.0  −7.0 to −3.0 −3.56 Rf Y (D65, 10°)  4% to 14% 5% to 9% 8.9%a*_(f) (D65, 10°) −20 to 0.0   −16 to −8.0 −15.9 b*_(f) (D65, 10°) 0.0to 10  0.0 to 8.0 2.92 SHGC </=0.40 </=0.35 0.371 SC </=0.49 </=0.460.43 Tuv </=0.35 </=0.30 0.297 Tuv Damage </=0.49 </=0.46 0.559 Weighted(ISO) IGU Solar Characteristics T Y (D65, 10°) >/=58% >/=60% 63.1%a*_(t) (D65, 10°) −10 to 0.0  −4.0 to −2.0 −1.87 b*_(t) (D65, 10°)   0to 4.0 2.0 to 4.0 2.08 Rg Y (D65, 10°)  4% to 20% 10% to 15% 15.9%a*_(g) (D65, 10°) −10 to 0.0  −4.0 to −1.0 −1.49 b*_(g) (D65, 10°) −10to 0.0  −7.0 to −3.0 −2.31 Rf Y (D65, 10°)  4% to 20% 10% to 15% 15.0%a*_(f) (D65, 10°) −20 to 0.0   −16 to −8.0 −9.09 b*_(f) (D65, 10°) 0.0to 10  0.0 to 8.0 2.28 SHGC </=0.35 </=0.30 0.329 SC </=0.43 </=0.400.38 U-value  0.20 to 0.30 0.22 to 0.25 0.24 Tuv </=0.30 </=0.25 0.248Tuv Damage </=0.49 </=0.46 0.501 weighted

Example Coater Set Up Temperable Test #38 Ar O2 N2 Pressure TemperableCathode Target Voltage (V) I (amp) P (kW) (sccm) (sccm) (sccm) (×10−³hPA) Reactive Gas:kW Annealed  1 SiAl 458.9 179.8 43.2 300 30 328 0 7.596.50  2 SiAl 463 178.1 43.3 300 30 328 3.53 7.58 6.51  6 SiAl 436.9195.8 43.7 300 30 328 3.45 7.51 6.43  5 ZnAl 439.8 129.2 34.2 150 330 02.02 9.65 11.95  7 ZnAl 325.8 160.6 34.6 150 330 0 1.1 9.54 0.00 10 Ag527.8 44.1 23.3 100 40 0 0.644 1.72 7.77 20 NiCr 532.4 47.9 25.5 100 1960 0.155 7.69 6.07 11 SiAl 558.4 161.8 39.1 300 30 264 3.86 6.75 6.13  4SiAl 476.9 163.2 38.8 300 30 264 2.65 6.80 6.10 12 SiAl 519.7 162.6 39300 30 264 5.09 6.77 6.13 13 SiAl 497.7 155.8 38.7 300 30 264 4.57 6.826.14 14 SiAl 410.9 182.6 38.6 300 30 264 4.07 6.84 6.15 15 SiAl 444.4165.9 38.7 300 30 264 1.15 6.82 6.15 16 SiAl 449.7 151.9 38.7 300 30 2644.93 6.82 6.15 17 SiAl 477.4 157.4 38.7 300 30 264 4.31 6.82 6.16 17ASiAl 474 160.3 38.4 300 30 264 0 6.88 13.09 18A ZnAl 366.9 168.5 34.8150 440 0 1.42 12.64 0.00 23 Ag 486.7 21.4 10.4 100 40 0 0.661 3.85 8.2419 NiCr 605.9 39.8 24.1 100 194 0 0.578 8.05 7.11 26 SiAl 461.2 141.332.8 300 30 257 3.46 7.84 7.08 27 SiAl 443.3 138.5 33 300 30 257 1.397.79 7.06 28 SiAl 445.6 136.8 32.8 300 30 257 5.38 7.84 7.09 29 SiAl435.2 145.5 32.4 300 30 257 4.37 7.93 7.08 30 SiAl 474.5 138.6 33 300 30257 4.14 7.79 7.06 18 C 506.9 123.7 30.9 500 0 0 3.78

Sample #521 AC31 Temperable Monolithic &IGU Mar. 16, 2007 SolarCharacteristics Characteristic Monolithic IGU T Y (D65, 10°) 69.3% 63.1%a*_(t) (D65, 10°) −1.13 −1.87 b*_(t) (D65, 10°) 1.95 2.08 Rg Y (D65,10°) 12.2% 15.9% a*_(g) (D65, 10°) −1.48 −1.49 b*_(g) (D65, 10°) −3.56−2.31 Rf Y (D65, 10°) 8.9% 15.0% a*_(f) (D65, 10°) −15.9 −9.09 b*_(f)(D65, 10°) 2.92 2.28 SHGC 0.371 0.329 SC 0.43 0.38 Tuv 0.297 0.248 TuvDamage Weighted (ISO) 0.559 0.501

While the present invention has been described with respect to specificembodiments, it is not confined to the specific details set forth, butincludes various changes and modifications that may suggest themselvesto those skilled in the art, all falling within the scope of theinvention as defined by the following claims.

1. A low-emissivity coating on a substrate, the coating comprising, inorder outward from the substrate: a first dielectric layer; a firstnucleation layer; a first Ag layer; a first barrier layer; a seconddielectric layer; a second nucleation layer; a second Ag layer; a secondbarrier layer; a third dielectric layer; and optionally, a topcoatlayer.
 2. The low-emissivity coating of claim 1, wherein at least one ofsaid first dielectric layer, said second dielectric layer or said thirddielectric layer is in sub-stoichiometric state.
 3. The low-emissivitycoating of claim 1, wherein at least one of said first barrier layer orsaid second barrier layer is an absorbing barrier layer.
 4. Thelow-emissivity coating of claim 1, wherein the first barrier layer andthe second barrier layer each separately comprise a material selectedfrom the group consisting of a metal, an alloy, a silicide, an absorbingoxide, and a nitride.
 5. The low-emissivity coating of claim 4, whereinthe first barrier layer and the second barrier layer each separatelycomprise a material selected from the group consisting of Ti, TiN, Si,NiCr, NiCrOx, Cr, Zr, Mo, W, and ZrSi.
 6. The low-emissivity coating ofclaim 5, wherein at least one of the first barrier layer and the secondbarrier layer comprises NiCr.
 7. The low-emissivity coating of claim 5,wherein at least one of the first barrier layer and the second barrierlayer comprises NiCrOx.
 8. The low-emissivity coating of claim 1,wherein at least one of the first or second barrier layers is capable oflowering transmission of the coating.
 9. The low-emissivity coating ofclaim 1, wherein at least one of the first or second barrier layers iscapable of increasing absorption of the coating.
 10. The low emissivitycoating of claim 1, wherein the second silver layer is thicker than thefirst silver layer.
 11. The low emissivity coating of claim 1, whereinthe first barrier layer is thicker than the second barrier layer. 12.The low emissivity coating of claim 10, wherein the ratio of the firstsilver layer thickness to the second silver layer thickness is about 0.8to about 1.2.
 13. The low emissivity coating of claim 11, wherein theratio of the first barrier layer thickness to the second silver barrierthickness is about 1.2 to about 2.0.
 14. The low emissivity coating ofclaim 1, wherein the first nucleation layer is thicker than the secondnucleation layer.
 15. The low emissivity coating of claim 14, whereinthe ratio of the first nucleation layer thickness to the secondnucleation layer thickness is about 1.2 to about 2.0.
 16. The lowemissivity coating of claim 1, wherein the third dielectric layer has anindex of refraction that is lower than both the index of refraction ofthe second dielectric layer and the index of refraction of the firstdielectric layer.
 17. The low emissivity coating of claim 7, whereineach of said barrier layers comprises a 2:1 oxygen:kw ratio.
 18. Thelow-emissivity coating of claim 1, wherein each of the first dielectriclayer, the second dielectric layer, and the third dielectric layerindependently comprises a material selected from an oxide, a nitride,and an oxy-nitride, or a combination thereof.
 19. The low-emissivitycoating of claim 18, wherein at least one of the first dielectric layer,the second dielectric layer, and the third dielectric layer comprises anoxide.
 20. The low-emissivity coating of claim 19, wherein the oxidecomprises up to about 20 wt % of an element selected from the groupconsisting of Al and B.
 21. The low-emissivity coating of claim 20,wherein the oxide comprises up to about 10 wt % of an element selectedfrom the group consisting of Al and B.
 22. The low-emissivity coating ofclaim 15, wherein at least one of the first dielectric layer, the seconddielectric layer, and the third dielectric layer comprises a nitride oran oxy-nitride.
 23. The low-emissivity coating of claim 1, wherein atleast one of the nucleation layers comprises ZnAlOx.
 24. Alow-emissivity coating on a substrate, the coating comprising, in orderoutward from the substrate: a first dielectric layer comprisingSiAlOxNy; a first nucleation layer comprising ZnAlOx; a first infraredreflecting layer comprising Ag; a first absorbing barrier layercomprising NiCr; a second dielectric layer comprising SiAlOxNy; a secondnucleation layer comprising ZnAlOx; a second infrared reflecting layercomprising Ag; a second absorbing barrier layer comprising NiCr; a thirddielectric layer comprising SiAlOxNy; and optionally, a topcoat layer.25. A low-emissivity coating on a substrate, the coating comprising, inorder outward from the substrate: a first dielectric layer comprisingSiAlOxNy; a first nucleation layer comprising ZnAlOx; a first infraredreflecting layer comprising Ag; a first absorbing barrier layercomprising NiCrOx; a second dielectric layer comprising SiAlOxNy; asecond nucleation layer comprising ZnAlOx; a second infrared reflectinglayer comprising Ag; a second absorbing barrier layer comprising NiCrOx;a third dielectric layer comprising SiAlOxNy; and optionally, a topcoatlayer.
 26. The low emissivity coating of claim 1, wherein the substrateis glass.
 27. A low-emissivity stack comprising at least one absorbingbarrier layer, said low-emissivity stack characterized by a solar heatgain coefficient (SHGC) that is less than about 0.31.
 28. Thelow-emissivity stack of claim 27, wherein the stack is characterized bya solar heat gain coefficient (SHGC) that is about 0.22 to about 0.25.29. The low emissivity stack of claim 27, wherein the stack has a lighttransmittance of about 42% to about 46%, as measured on an IGU.
 30. Thelow emissivity stack of claim 27, wherein the stack has a lighttransmittance of about 58% to about 62%, as measured on an IGU.
 31. Thelow-emissivity stack of claim 27, characterized by improved mechanicalor chemical stability.
 32. A method of making a low-emissivity stackhaving a low solar heat gain coefficient (SHGC), said method comprisingdepositing on a substrate the coating of claim
 1. 33. The method ofclaim 32, wherein the depositing comprises magnetron sputtering.
 34. Thelow emissivity stack of claim 1, characterized by a tolerance fortempering or heat strengthening.
 35. The low emissivity stack of claim34, wherein optical qualities of the stack are not degraded followingtempering or heat strengthening.
 36. The low emissivity stack of claim27, wherein the stack has a transmittance color with a negative a* and anegative b*.
 37. The low emissivity stack of claim 27, wherein the stackhas a transmittance color with a negative a* and a positive b*.
 38. Anautomotive window comprising the low emissivity coating of claim 1.